An electric automobile or a hybrid automobile mounts a motor as a power source for a vehicle thereon, and includes a power conversion device such as an inverter for controlling electric power to be supplied to the motor. The power conversion device includes a power module which incorporates a power semiconductor element such as an IGBT therein, a drive circuit which drives the power module, a control circuit for controlling these parts, and a current smoothing capacitor. Since these electronic parts are weak with respect to heat, it is necessary to cool these parts. In many cases, a large-capacity power conversion device with a large heat value is provided with a cooler having the water cooler structure for circulating cooling water therein.
Among the electronic parts which constitute the power conversion device, the power module is the part which has the largest heat value. To enhance cooling performance of the power module, the double-sided cooling structure which simultaneously cools both surfaces of the semiconductor element is effective. As an example of the double-sided cooling mounting structure of the power module, there has been known the structure described in patent literature 1.